Interval timer



Jan. 1, 1957 J. LEONARD INTERVAL TIMER Filed May 11, 1953 216 OR 00 SOURCE INVENTOR. JOHN L. LEONARD BY 42% M L W ATTORNEYS United States Patent INTERVAL TIMER John L. Leonard, San Diego, Calif.

Application May 11, 1353, Serial No. 354,438

7 Claims. (Cl. 317-142) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates generally to timing devices, and more specifically to an interval timer well suited to photographic, welding, and other similar arts, though not limited to such, it being applicable in almost any art wherein timed intervals are of importance.

It is an object of this invention to provide a reliable timing device in which a translating means is operated after a predetermined interval.

It is a further object of the invention to provide a timing device which is readily operable on either A.-C. or D.-C. voltage.

Still a further object is the provision of a variable interval timer simple and accurate in its adjustment.

It is still a further object of the invention to provide an interval timer having an almost instantaneous reset time.

It is a further object of this invention to provide an inexpensive timing device utilizing current flow as a metering means and having simple circuitry.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a schematic illustration of an electrical circuit in accordance with the present invention; and

Fig. 2 is a schematic illustration of a modification embodying the invention.

Referring to the figures of the drawings, a preferred physical embodiment of the invention is shown in Fig. 1, wherein the elements are shown in their normal unenergized state.

In this embodiment an impedance 11, having a capacitive reactance, is employed in conjunction with a variable resistance 12 and a gaseous electron discharge device, such as a neon diode tube 13, to control for a variable predetermined time interval the operation of a current translating device, relay 14, which includes transfer contact means comprising relay arm 21 and contacts 22 and 23 which in turn may control various other devices or operations, such as the energization of a load 18, etc.

The capacitive impedance 11 is arranged in parallel with gaseous diode 13 and the coil of relay 14. This forms a discharge loop for the capacitive impedance 11 upon its being charged to a critical value.

This discharge loop circuit is connected in series with a rectifier 15. This entire series-parallel circuit is connectible to a suitable source of potential, A.-C. or D.-C. through a manually operable double pole, double throw switch 16, and relay arm 21 alternatively in contact with either of relay contacts 22 or 23 (as described in operation hereinafter), and alternatively variable resistance 12 or resistance 17, repectively, depending on which of contacts 22 or 23 is in the circuit. A load 18 is connectible to the same or any other suitable source of potential through contact 22, contact arm 21 and switch contacts 31, 32.

Prior to operation in the unenergized state switch 16 is in position to close contacts 33, 34 (to be described in operation hereinafter). In this position of switch 16 the capacitive impedance 11 is completely discharged and relay arm 21 is in contact with contact 22, arm 21 normally being biased into engagement with this contact. No voltage is applied to the timing system and no current is flowing in the relay coil, and the load is deenergized.

When it is desired to energize the load 18, which may be an incandescent lamp or welder or otherwise as desired, for a predetermined time interval the switch 16 is moved to close contacts 31 and 32. This immediately closes a circuit supplying potential to the load 18 and begins a predetermined time interval at the end of which this circuit will be broken and the load will be deenergized. This predetermined period is determined primarily by the time constant of the capacitive impedance 11 and resistance 12, either or both of which may be varied to increase or decrease the time interval. Increasing the value of either of these elements will increase the time interval.

Upon the closing of contacts 31, 32, the capacitive impedance 11 begins to charge through resistance 12. At the beginning of this cycle the voltage drop appears primarily across the resistance 12, with no voltage drop across capacitive impedance 11, and thus no voltage across the electrodes of tube 13. The charge on capacitive impedance 11 gradually builds up through resistance 12 until it reaches the firing potential of tube 13. This ends the predetermined time interval, tube 13 thereupon firing and providing a low impedance path for the discharge of the capacitive impedance 11. This sudden flow of current in the discharge loop energizes the relay coil, thus opening contacts 21-22 and closing contacts 2123. This opens the load circuit and de-energizes the load 18. The closing of contacts 21, 23 establishes a relay holding circuit from the source of potential through rectifier 15, the coil of relay 14, resistance 17, relay contact 23, relay arm 21, switch contacts 31, 32 and return to the source of potential. The tube 13 is extinguished very shortly after the discharge of the condenser 11 therethrough begins as the voltage across the condenser, and thus the tube 13, decreases below the extinction potential of the tube 13.

To prepare the system for a new timing cycle the capacitive impedance 11 is completely discharged by manually moving the switch 16 to open contacts 31, 32 and to close contacts 33, 34. Opening switch contacts 31, 32 breaks the relay holding circuit and the relay contact arm 21 again establishes contact with contact 22, thus completing the cycle and readying the system for a new timing operation. It will be apparent that the reset time is almost instantaneous.

It will be apparent that if the timer is to be used on D.-C. voltage exclusively, the rectifier 15 may be omitted, if desired.

Fig. 2 shows a modification in which the variable resistance 12 is connected directly to switch 16 by line 19 (which line also connects contact arm 21 to the switch 16) instead of through relay contacts 21, 22 as in the embodiment of Fig. 1. Thus, when the switch 16 is moved to close contacts 31, 32, a circuit is set up from the potential source to rectifier 15, the parallel network 11, 14, 13, resistance 12, switch contacts 31, 32 and return to the source of potential, as well as a parallel circuit from the potential source through load 18, contact 22, contact arm 21, line 19, switch contacts 31, 32

and return to the potential source. At the end of the predetermined time interval the capacitive reactance 11 will discharge through relay 14 and tube 13, energizing relay 14 to thereby open contacts 2122 (thus deenergizing the load 18) and close contacts 2123, as in the embodiment shown in Fig. l. A holding circuit is thus established through rectifier 15, the coil of relay 14, resistance 17, contact 23, contact arm 21, line 19, and switch contacts 31, 32. Preparation for a new timing cycle is accomplished in the same manner as with the embodiment shown in Fig. l by moving the switch 16 to close contacts 33 and 34.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than. as specifically described.

Having described my invention, what is claimed is:

1. An interval timer of the character disclosed comprising a source of D. C. potential, a condenser and a resistor connected in series circuit across said source, a load connected across said series connected condenser and resistor, a current responsive translating means and a gaseous electron discharge device connected in series across said condenser, normally open manual switch means in said series circuit for energizing said load from said source and concurrently charging said condenser from said source through said resistor as the switch means is closed thereby to initiate a timing interval which is terminated when the voltage across the condenser has increased to a value suflicient to render said electronic discharge device conducting, and transfer and holding contact means included in said translating means and operable thereby for disconnecting said load from said source and transferring connection of said source across said load to connection and holding across the translating means as the translating means operates on current discharged from said condenser through said electron discharge device, whereby energization of the translating means is maintained until said manual switch means is returned to its normally open position.

2. An interval timer of the character disclosed comprising, in combination, a source of D. C. potential, a condenser and a resistor connected in series circuit across said source, a load connected across said series connected condenser and resistor, a current responsive translating means and a gaseous electron discharge device connected in series across said condenser, normally open manual switch means in said series circuit for energizing said load from said. source and concurrently charging.

said condenser from said source through said resistor as the switch means is closed thereby to initiate a timing interval which is terminated when the voltage across said condenser has increased to a value sufiicient to render said electron discharge device conducting, said condenser and resistor normally being connected in series across said source when said switch means is closed, and transfer and holding contact means included in said translating means and operable thereby for disconnecting said load from said source and transferring connection of said source across said load and across said series connected resistor and condenser to connection and holding across said translating means as the translating means operates on current discharged from said condenser through said electron discharge device, whereby energization of the translating means is maintained until said manual switch means is returned to its normally open position.

3. An interval timer as in claim 1 in which at least one of said resistor and condenser elements is adjustable to vary said timing interval.

4. An interval timer as in claim 1 wherein said translating means and said load are each connected on one side thereof to one side of said source and said contact means includes a first contact connected to the other side of said load, a second contact connected to the other side of said translating means, and a movable contact arm connected by said switch means to the other sideof said source, said translating means being a relay having said movable contact arm normally biased into engagement with said first contact and movable into engagement with said second contact as the relay operates upon energization thereof;

5. An interval timer as in claim 4 wherein said condenseris connected to said one side of the source, said resistor'is connected to the other side of said condenser, and the other side of said resistor is connected to said first contact.

6. An interval timer as in claim 4 wherein said condenser'is connected on one side thereof to said one side of the source and connected on the other side thereof to said resistor, said resistor being connected on the other side thereof to said movable contact.

7. An interval timer as in claim 4 wherein said switch means comprises a double pole, double throw switch, having a first pole connected to said contact arm and a firstcontact engageable by said pole and connected to said other side of said source and a second pole connected to said one side of the source and engageable with a second contactconnected to the junction of said condenser and said resistor.

References Cited in the file of this patent UNITED STATES PATENTS 

